Method of binding a plurality of sheets



March 18, 1969 H. N. STAATS ET AL 3,433,688

METHOD OF BINDING A PLURALITY OF SHEETS Filed Feb. 7, 1966 United States Patent 3,433,688 METHOD OF BINDING A PLURALITY 0F SHEETS Henry N. Staats, Deerfield, and John F. Winkelmann,

Mundelein, Ill., assignors to General Binding Corporation, Northbrook, 11]., a corporation of Illinois Filed Feb. 7, 1966, Ser. No. 525,547 US. Cl. 156-85 6 Claims Int.'Cl. B29c 29/00; 1332b 7/02 ABSTRACT OF THE DISCLOSURE A binding element and method of binding perforated sheets wherein the binding element comprises a backbone having fingers transversely extending therefrom which are curled from flattened shape into the final curled, paperbinding configuration, by a change in the environment surrounding the binding element, without the application of physical forming or bending forces to the binding element.

Plastic binding elements have long been known in the commercial and patented prior art. For example, attention is drawn to prior United States Patents Nos. 2,638,902 and 2,910,068 illustrating forms of plastic binding elements constructed with a backbone portion and a plurality of teeth projecting from one edge of the backbone. Such prior art binding elements have been constructed from sheet plastic material and are, in ordinary practice, rolled from a generally flat blank into a precurled cylindrical configuration wherein the projecting teeth or fingers lap the backbone. The resiliency of the plastic in such bindings permits unrolling of the binding element to permit insertion or removal of perforated sheets from the binding element.

The apparatus heretofore employed for uncurling such preformed generally cylindrical resilient binding elements is illustrated in prior patents such as those issued to H. Frederick No. 2,898,613 and P. J. Bardy No. 2,908,173.

As those familiar with the prior developments above mentioned are fully aware, the typical binding element commercially in use is purchased by the consuming public in a precurled form and is uncurled at the time of book assembly. It has, however, been the practice of some consumers to employ a combined curling and binding operation. In such systems, a relatively flat binding element having a plurality of projecting teeth or fingers is inserted into the perforations along one edge of a book and is simultaneously permanently formed, by mechanical dies, into the final, generally cylindrical configuration. Such combination curling and binding devices prove satisfactory in some installations but, due to their complicated construction, they are reserved mainly for large binderies handling a large Volume of bindings.

It is the purpose of the present invention to provide a novel binding element which may be commercially distributed in a flat, uncurled condition. The binding element of the present invention may readily be inserted into a book, or the like, being bound, by projecting the generally straight teeth or fingers thereof through the perforations of the book pages. Curling of the fingers and backbone of the binding element of the present invention is, however, accomplished automatically without the presence of dies, or other pressure devices. Instead, the curling action of the binding element is automatically self-induced in the binding element by the application of heat and the tendency of the binding to shrink on the inside surface thereof a substantially greater amount than the shrinkage at the outside. For example, it has been found that a surface shrinkage on the order of to less on one surface of a plastic sheet than on the opposite surface 3,433,688 Patented Mar. 18, 1 969 thereof is obtainable. By providing the surface of maximum shrinkage on the inside surface of the binding element, inserting the binding element into a perforated book or the like, and heating the assembly, the binding element will curl backwardly upon itself to provide an assembled binding and book combination. The present binding may, where desired, be automatically permanently self-sealed in the assembled condition in accordance with the present invention.

The unusual action of the binding of the present invention may be accomplished in several manners, in accordance with the principles of the present invention. All such techniques provide, however, a finger-shaped binding element having one surface thereof with a very materially different shrinkage or expansion coefiicient, or percent of dimensional change with environmental variation than the other. Accordingly, following insertion of the generally fiat finger, or fingers, constructed in accordance with the present invention, and the application of heat or other environmental change thereto, the binding element assumes the closed, curled condition. When employing plastic materials as the binding element, this curling accomplished by environmental change is preferably substantially irreversible, providing a stable curled binding element and book assembly.

It is, accordingly, an object of the present invention to provide a novel and extremely simple binding element and method of binding.

Another object of the present invention is to provide a novel, automatically self-curling binding element.

Still a further object of the invention is to provide a novel binding element.

Yet a further object of the invention is to provide an automatically self-sealing binding element.

A feature of the invention resides in the provision of a plastic binding element of varying surface shrinkage whereby a variation in environmental conditions will cause a dimensional change in the binding element.

Still other and further objects and features of the invention will become apparent to those skilled in the art from a consideration of the attached specification and drawings wherein one embodiment of the invention is shown by way of illustration only, and wherein:

FIGURE 1 is a generally isometric view of a looseleaf book bound by a self-actuating binding of the present invention.

FIGURE 2 is a generally isometric illustration of the binding element of the present invention in process of being applied to a looseleaf book or the like; and

FIGURE 3 is an end-elevational view of one form of binding element constructed in accordance with the principles of the present invention.

As may be seen from a consideration of the drawings, the binding element of the present invention comprises a longitudinally extending backbone 10 having a plurality of transversely extending teeth or finger elements 11. The fingers 11 are provided with pointed ends 12 and are of a width dimension slightly smaller than the width of the perforations 13 provided along and adjacent to the edge 14 of the cover and content sheets generally indicated at 15 and 16.

In assembling procedures, the fingers 11 are inserted by any conventional alignment means through the apertures 13 while the binding element is in the flat condition. Subsequent to insertion the thus assembled book and binding element are subjected to an environmental change capable of causing the binding to curl. This curling is accomplished in accordance with a principal embodiment of the present invention 'by providing the binding element per so constructed of a plastic laminate constructed of two layers of plastic having different shrink characteristics with a change in temperature. Thus, as shown in FIG- URE 3, the outermost layer a is comprised of a plastic having a shrink coeflicient substantially lower than that of the layer 10b. Accordingly, with the application of heat, layer 10b will shrink, and hence shorten its length relative to layer 10a causing the binding element to curl into a generally circular configuration as indicated at the dotted lines 100 in FIGURE 3.

It will, of course, be apparent that the characteristic of shrink is the opposite of the characteristic of expansion and that the primary consideration is one of selecting two different plastic materials having substantially different characteristics in this respect. It is, of course, possible to employ one material that expands upon heating as the outer member coupled with a material that is relatively stable upon heating, as well as employing an outermost member which is relatively stable coupled with an innermost member of material having a relatively high shrink characteristic. Similarly, it is noted that heat is a very suitable means for initiating or triggering the change in shape.

Our investigations have shown that several examples are satisfactory. For example, the layer 1012 may comprise polyvinyl chloride film laminated to a layer 10d of ABS. (acryl nitrite butadiene styrene) film. Such a combination shrinks, upon heating, to provide a curled element. Similarly, polyethylene may be laminated to polypropylene to provide a laminate that curls upon application of heat. While this latter product may tend to return to its original fiat condition upon a lowering in temperature, it may readily be heat-sealed while in the curled condition. Again, polyethylene may be laminated to Mylar of the type commercially marketed as heat shrinkable Mylar which has a high degree of shrink in the form of unrelieved biaxial stress inherently in the film as manufactured. Heat shrinkable Mylar is exemplary of a group of plastic film materials manufactured by holding the film in a stretched condition during the cooling step of its manufacture. Subsequent treating, such as heating, causes the material to remember its earlier state and, when unrestrained, to shrink upon relief of the stresses manufactured in the material. This last type of combination provides an excellent irreversible curling due to large shrinkage of the Mylar, or other prestressed heat shrinkable film or sheet.

In addition to the use of laminates, materials of a single sheet having one surface thereof stressed to shrink upon external energization, may be used. Commercially purchased sheet polyvinyl chloride has been found to exhibit an unbalanced shrink characteristic on opposing surfaces which may result from the orientation rolling or stretching operations performed on the material during its manufacture. Our invention clearly encompasses such materials.

It is preferred, for ease of utilization, that the laminated or dual stressed sheet material lie substantially flat at normal temperatures and curl upon heating or other treatment.

In the manufacture of binding elements, above described, in which the application of heat is employed to cause curling of the element, the binding may be self-sealing. One of a large number of adhesives of the type generally known as hot melt adhesives may be applied as a layer 10d to the inner surface of the element backbone (or to the outer surface of the fingers). Upon the heating of the element to its former temperature of approximately 180 F. or above, the stresses are relieved and it assumes the curled shape with the fingers contacting the backbone. The hot melt adhesive is chosen with a melting or surface activating temperature slightly below the freezing temperature of the base material. The temperature of melting or surface activation may be varied by well-known techniques such as the addition of permanent plasticizers compatible and/or copolymerizable with the base material. During the heating, the hot melt adhesive melts to provide an active adhesive permanently bonding the fingers to the backbone.

The temperatures of melting or surface activation may be varied by well known techniques such as the addition of permanent or nonvolatile plasticizers and/or resins compatible with the base material. For example, formulations using the following proportions are used:

Polyethylene, from 15 to 60 percent, preferably 40 to 55 percent Isobutylene polymeric material, from 10 to 35 percent,

preferably 20 to 30 percent Hydrocarbon resin, 20 to 60 percent More specifically, a formulation of 40 parts polyethylene, 20 parts of the above isobutylene material and 40 parts of the above hydrocarbon resin is combined to form a relatively low melting (e.g., substantially ll85 F.) adhesive of the hot melt class, which material is solid and relatively nontacky to the touch at room temperature, but which in a thin layer is sufficiently surface activated to effect bonding the fingers to the backbone during the heating and curling operation (e.g., in the case of a polyethylene-polypropylene laminate undergoing such curling at substantially F.).

Other hot melt adhesives are shown in Modern Plastics Encylopedia 1965 and Modern Plastics Encylopedia 1966. The plasticization of known ethyl cellulose with camphor, polyvinyl chloride and tricresyl phosphate and similar commercially available resin systems are selected for compatibility with the laminate elements being curled, with the resin-plasticizer proportions being adjusted (according to known techniques) to obtain the desired melting or surface activation temperature, in each instance preferably a few degrees below the curling temperature.

It will thus be seen that we have provided an improved binding element and method of binding that provides assembly substantially Without special tooling. Since variations may be made without departing from the scope of the novel concepts of our invention, we intend that the invention be limited solely by the scope of the hereinafter appended claims.

We claim as our invention:

1. The method of binding a plurality of sheets having aligned perforations therethrough which comprises the steps of:

providing a binding element having at least one substantially planar binding finger insertable into the perforations of the sheets, said binding element being formed of a material having a characteristic when subjected to a substantial change in temperature of curling without the application of an external force; inserting said binding fingers through the perforations of the sheets; and

substantially changing the temperature of said binding finger to cause the same to curl against the outermost of the sheets being bound.

2. The method of binding a plurality of sheets having aligned perforations therethrough which comprises the steps of:

providing a binding element having at least one substantially planar binding finger insertable through the perforation of the sheets, said binding element formed of at least two layers of laminated material with the material on one surface having a greater tendency to shrink than the material on the opposite surface when said binding is subjected to a substantial change in temperature;

inserting said binding fingers through the perforations of the sheets with the surface having the greater tendency to shrink projecting outwardly;

substantially changing the temperature of the binding element to cause said binding fingers to curl against the outermost sheets being bound.

3. The method of binding as defined in claim 1 further comprising:

bonding said curled binding finger subsequent to curling the same to permanently retain said binding finger in its curled configuration. 4. The method of binding as defined in claim 2 further comprising:

bonding said curled binding finger subsequent to curling the same to permanently retain said binding.

finger in its curled configuration. 5. The method of binding as defined in claim 2, further characterized by:

said binding element being formed of polyvinyl chloride film laminated to acryl nitrite butadiene styrene film. 6. The method of binding as defined in claim 4 further characterized by:

said binding element being formed of polyethylene film laminated to polypropylene film.

6 References Cited UNITED STATES PATENTS 2,106,419 1/ 1938 Anderson. 2,13 8,568 11/1938 Brandenberger 156-84 2,265,276 12/ 1941 Farkas. 2,273,824 2/ 1942 Barrett. 2,571,525 10/ 195 1 Blistein. 2,942,300 6/1960 Masters 264-230 X 2,930,054 3/ 1960 Bardy. 2,952,037 9/1960 Ruck et a1. 264230 X 3,000,057 9/1961 Swedlow et a1. 263-230 JEROME SCHNALL, Primary Examiner.

US. Cl. X.R. 1291; 15691; 264230, 249; 28121 

